107年 - 107 國立中山大學_碩士班招生考試_電波領域：電子學#108992

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申論題 (6)

(a)(20%) Draw the ac equivalent circuit. Deternine the frequency (in rad/s) at which the amplifier achieves the peak gain, and determine this maximum gain.

(b) (10%) Find the bandwidth of the amplifier (in rad/s). Note:for Q in saturation.

2. (20%) Use the Barkhausen criterion to determine the values of R and C so that the Wien-bridge circuit in Fig. 2 oscillates at 100 kHz.

(a) (20%) Determine the values of R and C in Fig. 3 so that the average power dissipation on resistor R is maximized.

(b) (10%) Calculate this maximum power.

4. (20%) An emitter follower in Fig. 4 is used to drive a very high impedance. Ci forms a high-pass filter with the divider resistances and the resistance looking into the base. Choose the value of C₁ so that the resulting cutoff frequency is 1 KHz.